cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-5 of 5 results.

A350931 Maximal determinant of an n X n Toeplitz matrix using the integers 1 to 2*n - 1.

Original entry on oeis.org

1, 1, 7, 105, 2294, 71753, 3051554, 175457984
Offset: 0

Views

Author

Stefano Spezia, Jan 25 2022

Keywords

Comments

Also maximal absolute value of the determinant of an n X n Hankel matrix using the integers 1 to 2*n - 1. - Stefano Spezia, Dec 22 2023

Examples

			a(2) = 7:
   [3    1]
   [2    3]
a(3) = 105:
   [5    1    3]
   [4    5    1]
   [2    4    5]
		

Crossrefs

Cf. A322908, A323254, A350930 (minimal).

Programs

  • Python
    from itertools import permutations
    from sympy import Matrix
    def A350931(n): return max(Matrix([p[n-1-i:2*n-1-i] for i in range(n)]).det() for p in permutations(range(1,2*n))) # Chai Wah Wu, Jan 27 2022

Extensions

a(5) from Alois P. Heinz, Jan 25 2022
a(6) from Pontus von Brömssen, Jan 26 2022
a(7) from Lucas A. Brown, Aug 28 2022

A350937 Minimal permanent of an n X n Toeplitz matrix using the integers 1 to 2*n - 1.

Original entry on oeis.org

1, 1, 7, 89, 2287, 89025, 5141775, 404316249
Offset: 0

Views

Author

Stefano Spezia, Jan 26 2022

Keywords

Comments

At least up to a(7) the minimal permanent is attained by a matrix which has 1, 3, 5, ... as first row and 1, 2, 4, 6,... as first column. - Giovanni Resta, Oct 13 2022
Also minimal permanent of an n X n Hankel matrix using the integers 1 to 2*n - 1. - Stefano Spezia, Dec 22 2023

Examples

			a(2) = 7:
    1    2
    3    1
a(3) = 89:
    1    2    4
    3    1    2
    5    3    1
		

Crossrefs

Cf. A322908, A323254, A350930, A350938 (maximal).

Programs

  • Python
    from itertools import permutations
    from sympy import Matrix
    def A350937(n): return 1 if n == 0 else min(Matrix([p[n-1-i:2*n-1-i] for i in range(n)]).per() for p in permutations(range(1,2*n))) # Chai Wah Wu, Jan 27 2022

Extensions

a(5) from Alois P. Heinz, Jan 26 2022
a(6) from Lucas A. Brown, Sep 04 2022
a(7) from Giovanni Resta, Oct 13 2022

A350953 Minimal determinant of an n X n symmetric Toeplitz matrix using the integers 1 to n.

Original entry on oeis.org

1, 1, -3, -12, -100, -1749, -47600, -800681, -39453535, -1351201968, -66984136299, -2938096403400, -235011452211680
Offset: 0

Views

Author

Stefano Spezia, Jan 27 2022

Keywords

Examples

			a(3) = -12:
    2    3    1
    3    2    3
    1    3    2
a(4) = -100:
    3    4    1    2
    4    3    4    1
    1    4    3    4
    2    1    4    3
a(5) = -1749:
    5    4    1    3    2
    4    5    4    1    3
    1    4    5    4    1
    3    1    4    5    4
    2    3    1    4    5
		

Crossrefs

Cf. A307887, A350930, A350954 (maximal), A356865 (minimal nonzero absolute value).

Programs

  • Python
    from itertools import permutations
    from sympy import Matrix
    def A350953(n): return min(Matrix([p[i:0:-1]+p[0:n-i] for i in range(n)]).det() for p in permutations(range(1,n+1))) # Chai Wah Wu, Jan 27 2022

Extensions

a(9) from Alois P. Heinz, Jan 27 2022
a(10)-a(12) from Lucas A. Brown, Sep 01 2022

A350932 Minimal determinant of an n X n Toeplitz matrix using the first 2*n - 1 prime numbers, with a(0) = 1.

Original entry on oeis.org

1, 2, -11, -286, -57935, -5696488, -1764195984, -521528189252
Offset: 0

Views

Author

Stefano Spezia, Jan 25 2022

Keywords

Examples

			a(2) = -11:
    2    3
    5    2
a(3) = -286:
    5    7    2
   11    5    7
    3   11    5
		

Crossrefs

Cf. A318173, A350930, A350933 (maximal).

Programs

  • Maple
    f:= proc(n) local i;
      min(map(t -> LinearAlgebra:-Determinant(LinearAlgebra:-ToeplitzMatrix(t)), combinat:-permute([seq(ithprime(i),i=1..2*n-1)]))) end proc:
    f(0):= 1:
    map(f, [$0..5]); # Robert Israel, Apr 01 2024
  • Python
    from itertools import permutations
    from sympy import Matrix, prime
    def A350932(n): return min(Matrix([p[n-1-i:2*n-1-i] for i in range(n)]).det() for p in permutations(prime(i) for i in range(1,2*n))) # Chai Wah Wu, Jan 27 2022

Extensions

a(5) from Alois P. Heinz, Jan 25 2022
a(6)-a(7) from Lucas A. Brown, Aug 27 2022

A358567 a(n) is the minimal determinant of an n X n Toeplitz matrix using the integers 0 to 2*(n - 1).

Original entry on oeis.org

1, 0, -2, -31, -1297, -39837, -2256911, -99518694
Offset: 0

Views

Author

Stefano Spezia, Nov 22 2022

Keywords

Examples

			a(2) = -2:
    [0, 1;
     2, 0]
a(3) = -31:
    [2, 3, 0;
     4, 2, 3;
     1, 4, 2]
		

Crossrefs

Cf. A350930 (integers from 1 to 2*n - 1), A358568 (maximal), A358569 (minimal permanent), A358570 (maximal permanent).

Extensions

a(5)-a(7) from Lucas A. Brown, Dec 03 2022
Showing 1-5 of 5 results.